In the production of corrugated cardboard boxes, the rotary die cutter processes a printed corrugated cardboard sheet for ruling and punching. The rotary die cutter includes an anvil cylinder and a knife cylinder which are juxtaposed to each other. In the punching process, a circular die board with a punching blade is installed around an outer periphery of the knife cylinder. The anvil cylinder and the knife cylinder are rotate in the opposite direction so that a sheet to be processed is fed to the cylinders where the sheet is punched out into a predetermined shape.
In the punching process, the punching scrap tends to stay between the punching blades. The punching scrap must be removed at a prescribed position to avoid scattering of the scrap.
Patent Document 1 (JP2005-7543A) and Patent Document 2 (JP2000-158389A) disclose devices for removing punching scrap for a rotary die cutter. The device disclosed in Patent Document 1 is described below in reference to FIG. 6 and FIG. 7.
In FIG. 6 and FIG. 7, the rotary die cutter 100 includes the anvil cylinder 102 and the knife cylinder 104. Both of the cylinders 102 and 104 rotate in the direction indicated with arrows in FIG. 6. The circular blade mount 106 is detachably installed around the outer periphery of the knife cylinder 104 by means of bolts or the like. The blade mount 106 includes a punching blade 108 for punching out the sheet S to be processed such as a corrugated cardboard sheet being fed between the cylinders 102 and 104 into a predetermined shape and holding teeth 110 for holding the punch scrap a from punching the sheet S by the punching blade 108.
A scrap dropping arm 112 is provided swingably around a support pin 114 on the outer periphery of the blade mount 106. The scrap dropping arm 112 has a notched portion 116 at a tip thereof so that the holding teeth can be inserted therein. A coil spring 118 is provided near the scrap dropping arm 112 and supported on a hinge member 120. A pressing piece 122 of the coil spring 118 is abutted on a surface of the scrap dropping arm 112 so as to press the scrap dropping arm 122 inwardly.
The knife cylinder 104 and the blade mount 106 have a plurality of through-holes 126 drilled therein in the radial direction. Each through-hole 126 has a push rod 130 inserted therein and covered by the scrap dropping arm 112. The push rod 130 is in contact with an outer periphery of an eccentric cylinder 132 which is installed inside of the knife cylinder 104. The eccentric cylinder 132 has a rotation center which is eccentric with respect to the center of the knife cylinder 104. The rotation of the eccentric cylinder 132 pushes the push rod 130 outwardly in the radial direction.
As shown in FIG. 6, the anvil cylinder 102 and the knife cylinder 104 rotate in the direction indicated with the arrows to feed the sheet S through the cylinders 102 and 104. The punching blade 108 mounted on the blade mount 106 forms a punching line on the sheet S. Inside of the punching line is a product part and outside of the punching line is punching scrap a. The product part is pushed out from the punching blade 108 by means of a spring member which is provided inside the punching blade 108 but not shown. The punching scrap a is held by the holding teeth 110 and transferred in the circumferential direction of the knife cylinder 104.
When the punching scrap a reaches a bottom part of the knife cylinder 103, the push rod 130 moves outwardly in the radial direction by the rotation of the eccentric cylinder 132. The scrap dropping arm 112 is swung outwardly to drop the punching scrap a from the holding teeth 110.
The push rod 130 is installed or removed by turning the scrap dropping arm 112 into the upright position. When the scrap dropping arm 112 is turned into the upright position, a stopper 124 and the pressing piece 122 mounted on a coil spring 118 are abutted on each other to inhibit the scrap dropping arm 112 from being turned more than need.
The punching scrap a needs to be pushed out at a predetermined position so as not to scatter the punching scrap which can interfere with operation of the rotary die cutter and cause the punching scrap to get in the product.
Patent Document 2 (JP2000-158389A) also discloses a punching scrap removal device, which has a pair of the rotary die cutters, each consisting of the anvil cylinder and the knife cylinder, installed in the traveling direction of the sheet to be processed. The rotary die cutter on the upstream side punches the sheet and the other rotary die cutter on the downstream side removes the punching scrap held in the punching blade.